Sheaths for implantable fixation devices

ABSTRACT

A sheath for organizing soft tissue includes a first tube having a flexible body sized and shaped to receive a fixation device, and a second tube coupled to the first tube having a flexible body sized and shaped to receive a soft tissue graft. A method for implanting soft tissue in a bone tunnel includes coupling a soft tissue graft to a sheath assembly; and positioning the sheath assembly relative to the soft tissue graft based on a measured depth of a bone tunnel. A set of surgical devices for implanting soft tissue grafts in a bone tunnel includes a sheath assembly, a measurement device for measuring the depth of the bone tunnel, a securing element configured to secure the sheath assembly to the soft tissue graft at a position determined by the measured bone tunnel depth, and a tensioning device configured to organize a plurality of soft tissue grafts.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application U.S. Ser. No.09/526,960 now U.S. Pat. No. 6,746,483, titled “SHEATHS FOR IMPLANTABLEFIXATION DEVICES,” filed Mar. 16, 2000.

BACKGROUND

The invention relates to devices that fix soft tissue to supportstructures, particularly devices that fix soft tissue grafts within bonetunnels.

In certain types of surgical procedures, soft tissue grafts must befixed within a bone tunnel. For example, in anterior cruciate ligament(ACL) replacement surgery, a ligament graft is harvested from thepatient or from a donor, and implanted within the knee by securing oneend within a bone tunnel drilled through the tibia, and the other endwithin a bone tunnel drilled through the femur. Several ACLreconstructive techniques are described in Rosenberg, U.S. Pat. No.5,139,520, which is incorporated herein by reference.

Referring to FIG. 1, a ligament graft 10 can be fixed within a bonetunnel using a bone screw 12. Graft 10 is made from e.g., a single ordouble long strip of soft tissue. To implant graft 10, the middle of thestrip (not shown) is first passed in a distal direction through a firsttunnel 14 in the tibia into a second tunnel 18 in the femur, and thenattached to the femur tunnel (or attached to bone adjacent the femurtunnel) with a femur fixation device (not shown). Two approximatelyequal length segments 19 a, 19 b of the graft extend proximally from theattached middle portion through tunnels 18 and 14. The two ends 20 a, 20b of segments 19 a, 19 b terminate proximal to tibial tunnel 14.Segments 19 a and 19 b of the graft are then fixed within tibial tunnel14 by inserting bone screw 12 between the two segments, such that shaft22 of the screw presses the segments against internal wall 24 of tunnel14.

In attaching soft tissue within a bone tunnel using a bone screw, it isimportant that the tissue be rigidly fixed within the tunnel to preventslippage. When the bone involved is relatively soft (less calcified), acommon problem in elderly patients, screws may not adequately fix thegraft to the bone.

SUMMARY

According to one aspect, the invention features a sheath for organizingsoft tissue including a first tube having a flexible body sized andshaped to receive a fixation device; and at least one second tubecoupled to the first tube. The second tube has a flexible body sized andshaped to receive a soft tissue graft.

Embodiments of this aspect of the invention may including one or more ofthe following features.

A securing element secures the second tube to the soft tissue graft. Thesheath includes a third tube coupled to the first tube having a flexiblebody sized and shaped to receive a soft tissue graft. At least one ofthe first tube and second tube is formed of a biocompatible materialselected from the group consisting of hydroxyapatite, polylactic acid,and polylactic glycolic acid. A guide is disposed within the second tubefor facilitating threading of soft tissue through the second tube. Aguide is disposed within the first tube for facilitating advancement ofa guide wire through the first tube. One end of the guide in the firsttube has a funneled shape.

The first tube and the second tube are integrally formed. The flexiblebodies of the tubes have strands that form a mesh structure. The strandsdefines spaces therebetween. The flexible bodies of the tubes include arelieved wall that is perforated and defines a plurality of holestherethrough. A major portion of the relieved wall is open. The flexiblebody of the second tube has two ends and each end has an opening. Thetwo openings are circular and have substantially the same dimensions.The first tube is smaller in diameter than the second tube.

According to another aspect, the invention features an assemblyincluding the sheath for organizing soft tissue and a fixation device.Embodiments of this aspect of the invention may include that thefixation device is a bone screw, and the flexible body of the first tubeis conformable to a shape of the shaft of the bone screw.

According to another aspect, the invention features a method forimplanting soft tissue in a bone tunnel. The method includes coupling asoft tissue graft to a sheath assembly; and positioning the sheathassembly relative to the soft tissue graft based on a measured depth ofa bone tunnel.

Embodiments of this aspect of the invention may include one or more ofthe following features.

The method includes inserting the soft tissue graft and the sheathassembly into the bone tunnel, and inserting a fixation device into thesheath assembly to fix the sheath assembly and soft tissue graft insidethe bone tunnel. The sheath assembly is fixed inside the bone tunnelsuch that an end of the sheath assembly is flush with an entrance to thebone tunnel. The method includes applying tension to the soft tissuegrafts during the insertion of the soft tissue grafts. The methodincludes organizing a plurality of soft tissue grafts so anapproximately equal tension can be applied to each graft.

Coupling a portion of a soft tissue graft includes inserting a portionof a soft tissue graft into the sheath assembly. The method includesproviding the sheath assembly with a first tube including a flexiblebody sized and shaped to receive a fixation device and at least onesecond tube coupled to the first tube and sized and shaped to receivethe soft tissue graft. The method includes inserting the fixationdevice, e.g., a bone screw, into the first tube to fix the soft tissuegraft inside the bone tunnel.

According to another aspect, the invention features a set of surgicaldevices for implanting soft tissue grafts in a bone tunnel. The setincludes a sheath assembly including a first tube and at least onesecond tube. The first tube is sized and shaped to receive a fixationdevice and the second tube is sized and shaped to receive a soft tissuegraft. The set includes a measurement device for measuring the depth ofthe bone tunnel; and a securing element configured to secure the sheathassembly to the soft tissue graft at a position determined by themeasured bone tunnel depth.

Embodiments of this aspect of the invention may include one or more ofthe following features.

The set includes a device configured to organize a plurality of softtissue grafts. The device includes a member having a first section and asecond section. The member is configured such that a first soft tissuegraft is securable to the first section and a second soft tissue graftis securable to the second section in response to manipulation of onlythe first section.

The securing element, e.g., a tie suture, is attached to the sheathassembly.

According to another aspect, the invention features a device forsecuring soft tissue grafts. The device includes a member having a firstsection and a second section. The member is configured such that a firstsoft tissue graft is securable to the first section and a second softtissue graft is securable to the second section in response tomanipulation of only the first section.

Embodiments of this aspect of the invention may include one or more ofthe following features.

The member includes a first knob disposed on the first section and asecond knob disposed on the second section. The first knob is knurledand manipulation of the first end is turning the first knob. A matingmember is disposed on the first section and is configured to mate withthe first knob. The second section includes a mating surface configuredto mate with the second knob. A first spring is positioned between themating member and first knob, and a second spring is positioned betweenthe mating surface and the second knob.

In an illustrated embodiment, a second member is coupled to the firstmember. The second member has a first section and a second section. Thesecond member is configured such that a third soft tissue graft issecurable to the first section and a fourth soft tissue graft issecurable to the second section in response to manipulation of only thefirst section.

The invention may include one or more of the following advantages.

The flexibility and thinness of certain implementations of the sheathallows the sheath to conform, e.g., to the shape of the fixation device,or to the shape of a bone tunnel.

The relief in the sheath, e.g., perforations in a wall of the sheath,allows in situ contact between a soft tissue graft and the wall of abone tunnel, promoting development of Sharpy-like fibers and permanentattachment of the soft tissue to the bone.

Therapeutic agents, such as osteoinductors or growth factors, can bedisposed on or embedded into the material of the sheath, allowingdelivery of the agent directly to the site of fixation.

Sheath implementations with multiple tubes allow multiple soft tissuegrafts to be fixed into a bone tunnel. The securing element may be usedto facilitate insertion of sheaths with multiple tubes by decreasing thearea of the cross-section of the inserted sheath and grafts, and byfixing the sheath in place on the grafts. Guide tubes may be used tofacilitate insertion of grafts into the flexible tubes of the sheaths.

The tensioner device allows tension to be equalized among multiplegrafts and organizes the grafts to permit easy introduction of afixation member. The tensioner device decreases the amount of workrequired to secure grafts by allowing two grafts to be secured to thetensioning device at opposite ends of the tensioning devicesubstantially simultaneously through the manipulation of only one knob.This allows the surgeon to hold two separate tendons and simultaneouslylock the tendons in place without requiring assistance from anotherperson.

Other implementations and advantages of the invention will be apparentfrom the following description and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a prior art technique of fixing a ligamentgraft within a tibial bone tunnel by using a bone screw;

FIG. 2A is a perspective view of a bone screw sheath;

FIG. 2B is a sectional view of the bone screw sheath of FIG. 2A;

FIG. 2C is a sectional view of the bone screw of FIG. 1;

FIG. 3 is a sectional view of a the bone screw and sheath of FIGS. 2A-2Cfixing a ligament graft within a bone tunnel in the tibia;

FIGS. 4 and 5 are sectional views illustrating alternative arrangementsfor the bone screw, sheath, and graft of FIG. 3 within the bone tunnelin the tibia;

FIG. 6 is a perspective view of an alternative embodiment of the sheathof FIG. 2A;

FIG. 7A is a perspective view of an alternative embodiment of the sheathof FIG. 2A that includes a washer;

FIG. 7B is a top view of the washer of FIG. 7A;

FIG. 8 is a perspective view of an alternative bone screw sheath thatincludes two tubes;

FIG. 9 is a perspective view of an alternative bone screw sheath thatincludes four tubes arranged to form a ring;

FIG. 10 is a perspective view of the bone screw sheath of FIG. 9 with anexternal sleeve;

FIG. 11 is a flow chart of a surgical process to implant and fix softtissue grafts in a bone tunnel using a sheath;

FIG. 12 shows a surgical kit used to implant and fix soft tissue graftsin a bone tunnel using a sheath.;

FIG. 13 is a perspective view of a sheath of the kit of FIG. 12;

FIG. 14 is a perspective view of a sheath assembly including the sheathof FIG. 13, guides, and a suture of the kit of FIG. 12;

FIG. 15A is a perspective view of an adjustable stop for a bone depthmeasurement device of the kit of FIG. 12;

FIG. 15B is a cross-sectional view of the adjustable stop of FIG. 15A;

FIG. 16 is a perspective view of a graft measurement and sheathpositioning assembly of the kit of FIG. 12;

FIG. 17 shows a scale extender element and ENDOBUTTON™ holder of the kitof FIG. 12;

FIG. 18 is a perspective view of a tensioning device of the kit of FIG.12 including a tie rod assembly and a handle;

FIG. 19 is an exploded view of the tie rod assembly of FIG. 18;

FIG. 20 is a cross-sectional view of a rod assembly of the tie rodassembly of FIG. 19;

FIG. 20A is a cross-sectional view of a mating plate of the rodassembly;

FIG. 20B is a cross-sectional view of a knob of the rod assembly;

FIG. 21 is a perspective view of the handle of FIG. 18;

FIG. 22 is a cross-sectional view of the handle of FIG. 21;

FIG. 23 shows an end piece of an inner shaft assembly of the handle ofFIG. 21;

FIG. 24 is a perspective view of a tensioning device holder of the kitof FIG. 12;

FIG. 25 is a detailed flow chart of a surgical process to implant andfix soft tissue grafts in a bone tunnel using a sheath;

FIGS. 26A and 26B illustrate the threading of tendons through the sheathassembly of FIG. 14;

FIGS. 27 illustrates the securing of two graft ends to the tensioningdevice of FIG. 18;

FIG. 28 illustrates the removal of the guides from the sheath assembly;

FIG. 29 illustrates the fixing of the sheath assembly to an additionalgraft using the suture;

FIG. 30 illustrates the securing of two additional graft ends to thetensioning device;

FIGS. 31A and 31B illustrate the tensioning of the grafts;

FIGS. 32-33B illustrate the positioning of the sheath assembly andgrafts within a knee joint; and

FIG. 34 is a cross-sectional view showing the sheath assembly and graftsfixed in position within the bone tunnel in the tibia.

DETAILED DESCRIPTION

Embodiments of the invention feature sheaths that surround bone screwsand soft tissue grafts to improve fixation of the grafts. In itssimplest form, the sheath is a flexible, mesh tube that surrounds onlythe bone screw, both the bone screw and the graft, or only the graft. Inother embodiments, the sheath includes multiple tubes.

Referring to FIGS. 2A-2C, a sheath 50 has a tube-shaped body 52 thatdefines a generally cylindrical exterior surface 53 and a generallycylindrical interior 54. Body 52 is formed from a biocompatible materialwoven into a mesh structure. The mesh defines numerous holes 56 thatexpose interior 54 to the outside. Sheath 50 also has two circular, openends 58 a, 58 b, allowing a tissue graft to pass entirely through theinterior of the sheath.

Interior 54 of sheath 50 is sized and shaped to receive bone screw 12.Sheath 50 has an internal diameter D₁ greater than the diameter D_(S) ofbone screw 12, so that both screw 12 and segments 19 a and 19 b of graft10 can fit snugly within the sheath. The sheath has a length L₁ slightlylarger than the length L_(S) of screw 12. The mesh body 52 is thin andflexible, allowing the sheath to adjust to snugly surround the screw;body 52 can be compressed to reduce the volume of interior 54, twisted,or stretched. Since sheath 50 is thin and flexible rather than rigid, itcannot on its own shore up soft bone, or fix a graft within a bonetunnel. (I.e., sheath 50 is not designed to be used alone as a fixationdevice or as a solid, rigid reinforcement of soft bone.)

In some embodiments, the threads forming the mesh body 52 are larger inthe radial direction than in the axial direction. This difference inthread size results in sheath 50 being less flexible radially thanaxially. In these embodiments, the diameter D₁ is more resistant toexpansion or contraction than length L₁. In other embodiments, thethread size is equal throughout body 52.

Diameter D₁ is, e.g., between about 8 and 10 mm, and L₁ is, betweenabout 25 and 40 mm. If sheath 50 is designed for a 7×25 bone screw (7 mmdiameter, 25 mm length), then L₁ is, e.g., about 30 mm, and D₁ is, e.g.,about 9 mm. Most of exterior surface 53 is open. For example, about 40%of the area exterior surface 53 is mesh strands, and about 60% is holes56. The thickness T₁ of the mesh wall of sheath 50 is, for example, lessthan about 0.3 mm, e.g., about 0.1-0.2 mm.

Body 52 can be made from a variety of bioabsorbable materials, includingpolylactic acid, or polylactic glycolic acid. Alternatively, body 52 canbe made from a blend of absorbable materials, or from a non-absorbablematerial, such as a polyester. The material forming the body preferablyhas a higher coefficient of friction than graft 10, so that exteriorsurface 53 of the sheath grips internal wall 24 of bone tunnel 14 morefirmly than graft 10 alone, improving fixation.

Body 52 can be formed, e.g., by weaving, braiding, knitting, orcrocheting strands of the material to form the cylindrical shape, or byextrusion, using techniques known in the art. The strands forming body52 have diameters of about 0.1-1.0 mm, e.g., 0.4-0.6 mm, or 0.51 mm.

Although sheath 50 can be used with a variety of fixation screws, screw12 preferably has blunt or rounded screw threads, as opposed to sharpthreads, so that the threads do not cut the sheath or the soft tissuegraft. A typical rounded-thread screw is shown in Roger et al., U.S.Pat. No. 5,383,878, which is incorporated herein by reference.

Referring to FIG. 3, in operation, a surgeon first forms bone tunnels 14and 18 within the tibia and femur, respectively. Next, graft 10 is fixedto the femur tunnel using any technique known in the art (not shown).For example, the femur fixation device can include a loop attached tothe femur at a distal end of femur tunnel 18. End 20 a of the graft ispassed distally through tunnels 14 and 18, passed through the loop, andthen pulled proximally through tunnels 18 and 14 until the middleportion of the graft is centered on the loop. Alternatively, the graftcan be threaded through the loop prior to implantation of the loop. Inaddition, rather than using a loop, one end of graft 10 can be fixedwithin the femur tunnel, allowing the other end to extend proximallythrough tunnels 18 and 14. To increase the number of segments availablefor fixation, multiple strips of soft tissue (i.e., multiple grafts) canbe separately attached to the femur. Various techniques for attaching agraft within a bone tunnel are described in Ferragamo, U.S. Pat. No.5,769,894, which is incorporated herein by reference, and in Rosenberg,supra.

After attaching graft 10 within (or adjacent to) femur tunnel 18, thesurgeon passes ends 20 a, 20 b of graft 10 through interior 54 of sheath50 (via open ends 58 a and 58 b), and then slides sheath 50 into tibialtunnel 14. The diameter of tunnel 14 is only slightly larger than theouter diameter of sheath 50, such that sheath 50 fits snugly withintunnel 14. Alternatively, sheath 50 can be inserted into tunnel 14 priorto passing the graft through the sheath. To insert sheath 50 into tibialtunnel 14, the surgeon can use a delivery tool, such as a rigid tubedetachably fixed to the distal end of the sheath. Alternatively, asuture can be threaded through the distal end of sheath 50, and thesheath can be pulled into place within tunnel 14 using the suture.

The surgeon then inserts bone screw 12 into interior 54 of sheath 50,between segments 19 a and 19 b of the graft. The screw may be insertedusing an insertion tool known in the art, such as a screw driver. Whenscrew 12 is in place as shown in FIG. 3, the screw presses segments 19 aand 19 b of the graft against the interior surface of sheath 50, andpresses exterior surface 53 of the sheath against wall 24, fixing thegraft within the tunnel.

As shown in FIG. 3, when screw 12 is inserted, it will typically beslightly off center, such that the screw's threads dig into wall 24 ofbone tunnel 14 along a segment 24 a of wall 24. For example, if screw 12has a major diameter of 9 mm, and a minor diameter of 7 mm, then thescrew threads will dig into wall 24 by about 1 mm along segment 24 a,where segment 24 a is about 120 degrees. This engagement of the threadswith segment 24 a of the wall helps hold screw 12 within tunnel 14, andtherefore improves fixation of graft 10 within the tunnel.

The presence of sheath 50 within bone tunnel 14 improves fixation ofgraft 10. Since exterior surface 53 of sheath 50 has a highercoefficient of friction than graft 10, sheath 50 is less likely thangraft 10 (which is made of tissue) to slide along wall 24 of the tunnel,or to twist when screw 12 is inserted into the tunnel. In addition,since body 52 of sheath 50 has a mesh structure, portions of graft 10protrude through holes 56 of the mesh, resisting sliding of graft 10relative to sheath 50. The flexibility of sheath 50 allows the sheath toconform to the shape of wall 24, maximizing the surface area contactbetween the exterior surface of the sheath and wall 24, therebyincreasing frictional forces between the sheath and the wall.

After screw 12 has been inserted into tunnel 14, the surgeon may trimthe portions of segments 19 a and 19 b that extrude proximally fromtunnel 14, completing the surgical procedure. Over time, graft 10permanently affixes to wall 24 by growth of Sharpy-like fibers betweenthe soft tissue of graft 10 and the bone tissue of wall 24.(“Sharpy-like fibers” are collagenous fibers that grow from bone into asoft tissue graft. The presence of Sharpy-like fibers indicate good bonygrowth to the graft, and therefore good fixation. See Pinczewski et al.,“Integration of Hamstring Tendon Graft With Bone in Reconstruction ofthe Anterior Cruciate Ligament,” Arthroscopy, 13: 641-43 (1997). Theopen holes 56 in body 52 of the sheath facilitate permanent fixation byincreasing the direct contact between the graft and the bone tunnelwall. Sheath 50 eventually dissolves, and new bone grows to fill itsposition.

To accelerate bone growth and permanent attachment of graft 10 to wall24, sheath 50 can include an osteoinductive agent, such ashydroxyapaptite, tricalcium phosphate, calcium sulphate, or a “ceramic”(a calcium and potassium crystalline). The osteoinductive agent can beapplied to sheath 50 prior to surgery by, e.g., spraying the sheath withthe agent, by dipping the sheath into a bath that includes the agent, bydusting or spraying the agent onto the sheath, or by filling the sheathwith a gel that includes the agent. In addition, the strands of materialforming the mesh body 52 can be hollow, and the agent can be within thehollow interiors of the strands. Alternatively, the agent can beincorporated into the material that forms body 52. For example, theagent can be blended into the material used to make the threads thatform mesh body 52, or can be added to the fibers as an osteoinductivefelt.

Other therapeutic agents, such as growth factors (e.g., tissue growthfactor or platelet derived growth factor), bone morphogenic proteins,stem cells, osteoblasts, and cytokines, can also be included in thesheath. These bioactive agents can be added using the techniquesdescribed above, or can be blended into the material that forms body 52using micro-encapsulation or nanoparticles. For example, body 52 can beformed from a material comprising microspheres of the agent and apolymer, such as polylactic glycolic acid. The microspheres of the agentand polymer can be prepared using known techniques. See, e.g., Cohen etal., “Controlled Delivery Systems for Proteins Based onPoly(Lactic/Glycolic Acid) Microspheres,” Pharm. Research, 8:713-20(1991); DeLuca et al., U.S. Pat. Nos. 5,160,745 and 4,741,872. Ratherthan forming microspheres, the agent and polymer can also be mixedtogether using, e.g., sintering techniques. See, Cohen et al.,“Sintering Techniques for the Preparation of Polymer Matrices for theControlled Release of Macromolecules,” J. Pharm. Sciences, 73:1034-37(1984). The bioactive agents can also be attached to body 52 usingadhesives or electrical charge, or can be directly loaded onto thesheath by a delivery mechanism after implantation of the sheath.

Other embodiments are within the scope of the claims. For example, thesheath can be used to assist fixation of a bone screw within the femurtunnel 18, in addition to the tibial tunnel 14.

Referring to FIG. 4, screw 12 can be placed between sheath 50 and wall24 of tunnel 14. In this embodiment, rather than inserting screw 12 intothe sheath after placement of the sheath within tunnel 14, screw 12 isinserted into tunnel 14 along the side of the sheath. To hold screw 12to the side of the sheath, the sheath can optionally include an externalloop 102. Loop 102 has a diameter slightly larger than the diameter ofscrew 12, so that shaft 22 of screw 12 fits snugly within the loop. Loop102 can be made from the same material as body 52, or can be made froman inflexible, rigid material.

When screw 12 is inserted, it compresses graft 10 within the sheath, andpresses exterior surface 53 of the sheath against wall 24, fixing graft10 within tunnel 14.

Referring to FIG. 5, segments 19 a and 19 b of graft 10 can bepositioned radially outside of sheath 50. In this embodiment, whensheath 50 is inserted into tunnel 14, it is located between ends 19 aand 19 b of the graft, so that the graft surrounds the sheath, ratherthan the sheath surrounding the graft. Screw 12 is then inserted intothe sheath, pressing segments 19 a and 19 b between exterior surface 53of the sheath and wall 24, fixing the graph in place. Alternatively, thescrew can first be inserted into the sheath, and then the sheath andscrew together can be positioned within the bone tunnel.

The structure of the bone screw sheath can be modified as well. Thediameter D₁, length L₁, and thickness T of the sheath can be varied toaccommodate different sized bone tunnels, different sized screws, anddifferent deployment methods. For example, in the deployment method ofFIG. 5, the inner diameter D₁ of the sheath can be approximately equalto the diameter D_(S) of the screw shaft, so that the screw fits verysnugly within the sheath, and exterior surface 53 of the sheath conformsto the shape of the screw shaft.

In the deployment methods shown in FIGS. 4 and 5, the sheath need not bemore rigid in the radial direction than in the axial direction. Thethreads forming the mesh body, therefore, are generally the same size inboth the radial and axial directions. In addition, sheaths used in thedeployment method of FIG. 5 can have less open space than sheaths usedwith the method of FIGS. 3 or 4. (I.e., less than 60% of the sheath'ssurface area will be holes.)

If the bone is particularly soft, sheath 50 can be woven tighter, sothat the sheath is less flexible, thereby providing a more firmsubstrate for screw 12 to engage.

The sheath need not have a mesh structure. For example, the sheath canhave a solid body with holes cut through the body, allowingcommunication between the exterior and interior of the sheath. Inaddition, the sheath's body need not be integrally formed. For example,the body can be formed by winding a strip of material around animplantable device to form a relieved body that defines an interior.

The sheath can have relief structures other than holes to allowcommunication between the exterior and interior. For example, othertypes of perforations, such as slits, can be used, instead of holes. Inaddition, the device can have a solid wall with thinned sections. Whenimplanted, the thinned sections biodegrade more quickly than othersections of the wall, such that in situ, the device developsperforations.

To increase the coefficient of friction of exterior surface 53 toimprove fixation of the sheath within the bone tunnel, exterior surface53 can have a roughened finish.

Referring to FIG. 6, rather than having two open circular ends, sheath150 has an open end 158 a and a closed end 158 b. Closed end 158 b givessheath a “bag” or “sock” shaped structure.

Referring to FIG. 7A, a sheath 250 includes a washer 280 attached to theproximal end 282 of the sheath. The washer 280 has a diameter D₂ that islarger than diameter D₁ of sheath 250, and is larger than the diameterof the bone tunnel. Washer 280 prevents proximal end 282 of the sheathfrom passing into the bone tunnel when the screw is inserted into thesheath, thereby ensuring that the sheath is ultimately positioned aroundthe screw shaft, rather than in front of the screw. Rather than beingcircular, the washer can be square, triangular, or any other shape, solong as it has a dimension larger than the diameter of the bone tunnel.Referring to FIG. 7B, the upper surface 284 of the washer can includeteeth or spikes 286 to grip bone, thereby reducing twisting of sheath250 when a bone screw is inserted into the sheath. The washer can bemade from a bioabsorbable material, or a non-absorbable, biocompatiblematerial. In operation, the washer can be detached from the sheath afterimplantation of the graft and bone screw, or can be left attached to thesheath.

Referring to FIG. 8, a sheath 350 includes two contiguous, parallel meshtubes, 352 a and 352 b. Tubes 352 a and 352 b are integrally woven,braided, knitted, or crocheted from threads. Each tube has a diameter D₃that is slightly larger than diameter D_(S) of screw 12, and slightlyless than diameter D₁ of sheath 50. Diameter D₃ can be, e.g., 2 mm, 4mm, 6 mm, or 8 mm. Sheath 50 has a length L₃ approximately equal to thelength of a fixation screw, e.g., about 10-50 mm, or 20-35 mm. The walls354 a, 354 b of tubes 352 a and 352 b each have a thickness of, e.g.,between 0.1 mm and 1.0 mm.

In operation, a soft tissue graft is passed through one of the tubes(e.g., tube 352 a), and the fixation screw is inserted into the secondtube (e.g., tube 352 b). When the sheath, graft, and fixation screw arepositioned within the bone tunnel, tube 352 a is compressed between thescrew and a wall of the bone tunnel. The graft, therefore, is compressedwithin tube 352 a, fixing the graft within the bone tunnel.

Referring to FIG. 9, a sheath 450 includes four parallel mesh tubes, 452a, 452 b, 452 c, and 452 d. The four tubes are arranged to form a ring454. Ring 454 defines a central cavity 456 disposed between the tubes.The cavity defines an axial bore that is coextensive with the axiallengths of each of the tubes.

Each tube 452 a, 452 b, 452 c, and 452 d has a diameter D₄ and a lengthL₄ similar to diameter D₃ and length L₃ of sheath 350 (FIG. 8). As withsheath 350, the tubes of sheath 450 are integrally woven.

In operation, segments of a soft tissue graft are passed through each oftubes 452 a-452 d. The surgeon can either use multiple, independenttissue grafts separately attached to the femur tunnel, or can split theproximal end of a single graft into four separate segments. The sheathis then inserted into the tibial bone tunnel, and a fixation screw isinserted into central cavity 456. When the sheath, soft tissue, andscrew are in place within the bone tunnel, the tubes are compressedbetween the screw and the bone tunnel wall, and the soft tissue segmentsare compressed within each tube, thereby fixing the soft tissue withinthe bone tunnel.

In the embodiment shown in FIG. 9, sheath 450 includes four tubesforming a ring. The sheath need not, however, be limited to this number.For example, the sheath can include a ring of 3, 5, 6, 7, or 8 tubes. Inaddition, soft tissue need not be passed through each tube. For example,soft tissue segments can be passed through two tubes, leaving theremaining tubes unoccupied.

Instead of being integrally woven, the tubes of sheath 450 can be woven,braided, or knitted separately, and attached together using, e.g.,stitching, spot welding, or an adhesive. The tubes can also be solidrather than mesh, and need not all have the same diameter. In addition,unlike the single tube sheaths of FIGS. 2A, 6, and 7, sheath 450 can berigid, rather than flexible.

Referring to FIG. 10, sheath 550 is identical to sheath 450 in allrespects, except that sheath 550 further includes a mesh sleeve 580 thatsurrounds the four tubes 552 a-552 d. Sleeve 580 is axially coextensivewith tubes 552 a-552 d, and is integrally woven with the four tubes.Alternatively, sleeve 580 can be a separate solid or mesh structureadhesively bound or otherwise coupled to the four tubes. Sleeve 580 actsto stabilize sheath 550, and facilitates insertion of the sheath intothe bone tunnel. For example, to insert sheath 550, a suture or deliverytool can be attached to sleeve 580, rather than directly to one of thetubes.

FIG. 11 shows a flow chart of a surgical process 600 to implant and fixsoft tissue grafts in a bone tunnel using a sheath. After soft tissuegrafts have been harvested in the usual fashion or otherwise acquired,the soft tissue grafts are coupled to the sheath (602), e.g., byinserting the grafts into the sheath and/or placing the grafts adjacentto the sheath. Concurrent, subsequent, or prior to coupling the graftsto the sheath, the bone tunnel depth is measured (604).

The position of the sheath relative to the grafts is adjusted inaccordance with the measured depth of the bone tunnel (606). Adjustmentof the position of the sheath ensures that the sheath, once insertedinto the bone tunnel, is properly positioned in the bone tunnel toreceive the fixation device used to fix the grafts and sheath in thebone tunnel. For example, when the fixation device is a typicalinterference screw, the sheath is preferably placed such that one end ofthe sheath is flush with the entrance of the bone tunnel. Once properlypositioned, the sheath is fixed to the grafts to prevent movement of thesheath relative to the grafts during insertion into the bone tunnel(608) and after fixation of the sheath and graft assembly in the bonetunnel.

After insertion of the sheath and graft assembly into the bone tunnel, afixation device, e.g., a bone screw, is inserted into the bone tunneland is received by the sheath to fix the sheath and graft assembly inthe bone tunnel (610) In another implementation, the graft is insertedfirst into the bone tunnel, and the sheath is subsequently pushed upinto the tunnel using an insertion tool.

More than one sheath can be coupled to a given graft and positionedrelative to the graft in accordance with the bone tunnel depth. Forexample, in ACL replacement surgery, a first sheath coupled to thegrafts is positioned within the femoral side tunnel, and a second sheathcoupled to the grafts is positioned within the tibial side tunnel.

Referring to FIG. 12, a surgical kit 700 used to implant and fix softtissue grafts in a bone tunnel includes a sheath 702 that is part of asheath assembly 703, a measurement device 704 with an adjustable stop706 for measuring the depth of a bone tunnel, a graft positioning board708 with an ENDOBUTTON™ holder 709 for facilitating coupling of sheath702 to the grafts and adjusting the position of sheath 702 relative tothe grafts, and a tensioning device 712 mounted to a holder 714, whichis coupled to board 708. The position of sheath 702 relative to thegrafts can be adjusted while the grafts are held in place by tensioningdevice 712. ENDOBUTTON™ holder 709 includes a scale member 711 and ascale extender element 710 for measuring the length of the grafts toproperly position the sheath in accordance with the measured bone tunneldepth.

After insertion of the sheath and the grafts into the bone tunnel, ascrew driver 716 is used to insert a screw 718 into the bone tunnel.Screw 718 is preferably tapered to facilitate insertion into sheath 702and has blunt or rounded screw threads, as opposed to sharp threads, sothat the threads do not cut sheath 702 or the soft tissue graft. Twoscrews 718 are included in kit 700, e.g., a 7×9×30 bone screws (7 mmsmaller diameter, 9 mm larger diameter, and 30 mm length) and an 8×10×30bone screws (8 mm smaller diameter, 10 mm larger diameter and 30 mmlength). The operator selects which bone screw to use based upon graftsize, tunnel size, and bone quality.

Referring to FIG. 13, sheath 702 includes three contiguous, parallelmesh tubes, 752 a, 752 b, and 752 c. Tubes 752 a, 752 b, and 752 c canbe, e.g., integrally woven, braided, knitted, or crocheted from threads.Alternatively, tubes 752 a, 752 b, and 752 c can be separately woven,knitted, or crocheted but otherwise coupled together (e.g., by a sutureor a sleeve). Tubes 752 a and 752 b have a diameter D₁ that is largeenough to comfortably allow passage of a typical soft tissue graft(e.g., 5 mm). Tubes 752 a and 752 b need not have the same diameter andmay be sized in relation to the diameter of the soft tissue graftdesignated to pass through each tube. Tube 752 c has a diameter D2 largeenough to allow passage of a guide wire used to guide a fixation device,e.g., a screw 718, into the bone tunnel (e.g., 2-3 mm).

Sheath 702 has a length L₁ in the range of, e.g., approximately one halfthe length of screw 718 to approximately the length of screw 718 (e.g.,15-30 mm when the screw length is 30 mm). In some implementations, tubes752 a, 752 b, and 752 c can have different lengths. The walls 754 a, 754b, and 754 c of tubes 752 a, 752 b, and 752 c, respectively, each have athickness of, e.g., between 0.1 mm and 1.0 mm.

Sheath 702 can be made from similar materials as described in referenceto body 52. The material and configuration of tube 752 c provides enoughflexibility to allow tube 752 c to expand from a first diameter selectedfor passage of a guide wire (e.g., 2-3 mm) to a second diameter largeenough to allow passage of screw 718 (e.g., 9-10 mm).

In another implementation, sheath 702 includes four outer tubes that arecircumferentially disposed around a central tube. The four outer tubesare similar in structure to tubes 752 a or 752 b, and the central tubeis similar in structure to tube 752 c. In use, four soft tissue graftsare passed through the four outer tubes, and a fixation device isinserted into the central tube.

In yet another implementation, sheath 702 includes a first tube disposednext to a second tube. The first tube is similar in structure to tubes752 a or 752 b, and the second tube is similar in structure to tube 752c. In use, a single soft tissue graft is passed through the first tube,and a fixation device is inserted into the second tube.

In yet another implementation, the diameter of tube 752 c is equal tothe diameter of tubes 752 a and/or 752 b. The diameter of tube 752 c canbe slightly larger than the smaller or larger diameter of screw 718(e.g., 7 mm or 9 mm).

Referring to FIG. 14, sheath assembly 703 includes the sheath 702, threeguides 756 a, 756 b, and 756 c, and a securing element, e.g., a suture758. Guides 756 a, 756 b, and 756 c fit within tubes 752 a, 752 b, and752 c, respectively. The outer diameter D₁ of guides 756 a and 756 b isslightly less than diameter D₁ of tubes 752 a and 752 b, respectively.Guides 756 a and 756 b define through channels 753 a and 753 b,respectively, each having a diameter large enough to allow passage oftypical soft tissue grafts (e.g., approx. 5 mm). The length L₁ of guides756 a and 756 b is, e.g., equal to, or preferably greater than thelength L₁ of tubes 752 a and 752 b of sheath 702. Guides 756 a and 756 bare formed from, e.g., a biocompatible plastic material (e.g., a polyether-block co-polyamide polymer such as PEBAX™) and thus facilitateinsertion of soft tissue grafts into tubes 752 a and 752 b by preventingtubes 752 a and 752 b from collapsing or otherwise closing andobstructing graft insertion.

The outer diameter D2 of guide 756 c is slightly less than diameter D2of tube 752 c. Guide 756 c defines a through channel 753 c having adiameter large enough to allow passage of a typical guide wire (e.g.,approx. 2-3 mm). Guide 756 c preferably has a funneled end 757 with adiameter D3 that facilitates insertion of the guide wire into tube 752c. Guide 756 c has a length L2, which is longer than that of the sheathand guides 756 a and 756 b. Guide 756 c is formed from a biocompatibleplastic material that is the same as or different than that of guides756 a and 756 b.

Once the grafts are coupled to sheath 702, and sheath 702 is properlypositioned relative to the grafts in accordance with the measured bonetunnel depth, as described further below, suture 758 is used to fixsheath 702 in position. The tie suture is, e.g., woven into, braided, orotherwise coupled to flexible mesh tubes 752 a, 752 b, and/or 752 c.

Referring to FIGS. 12, 15A and 15B, measurement device 704 includes ahandle 705, a rod 707 extending from handle 705, and an adjustable stop706 having a cylindrical body 760 defining a cylindrical channel 762 forslidably receiving rod 707. Body 760 defines a groove 765 at an end 766of channel 762 in which an o-ring 764 is positioned to ensure a snugfit. Body 760 also defines a radial, threaded hole 770 into which athumb screw 767 with an engaging end 768 is inserted. Thumb screw 766 isfixed in place by a set screw 772 inserted in a hole 774 defined by awall 776 of cylindrical body 760.

Referring to FIG. 16, a graft measurement and sheath positioningassembly 800 of kit 700 includes the graft positioning board 708 withattached ENDOBUTTON™ holder 709 and scale extender element 710,tensioning device holder 714, and tensioning device 712 mounted toholder 714.

Referring also to FIG. 17, scale member 711 of ENDOBUTTON™ holder 709includes an ENDOBUTTON™ coupler 808 and a pin 806 for attachingENDOBUTTON™ holder 709 to board 708. Scale extender element 710 includesa hollow rectangular housing 850 sized and shaped to receive scalemember 711 of ENDOBUTTON™ holder 709. Housing 850 includes arms 854 thatnormally protrude into the interior of the housing and are pushedoutwards by scale member 711. The frictional engagement of 711 againstarms 854 secures scale member 711 within scale extender element 710.Soft tissue grafts of a typical length (e.g., 120 mm), which otherwisewould extend beyond the length of scale member 711 of the ENDOBUTTON™holder 709 (e.g., 70 mm), are positioned on and mechanically supportedby the scale extender element 710.

Referring again to FIG. 16, tensioning device holder 714 is coupled toboard 708 by a coupler 812 that rides in a guide rail 814 defined inboard 708. Tensioning device holder 714 is movable in the direction ofarrow A along guide rail 814 to place grafts coupled to loop 804 undertension, and can be fixed in place using a screw 813 of coupler 812.

Referring to FIG. 18, the tensioning device 712 includes a tie rodassembly 870 coupled to a handle assembly 872. Tie rod assembly 870includes a frame 874 that connects two parallel rod assemblies 876.Frame 874 defines a hole 878 bisected by an arch 880. Frame 874 includestwo parallel hollow tubes 875 that receive rod assemblies 876, which areattached to tubes 875 by pins 882.

Referring to FIGS. 19 and 20, each rod assembly 876 includes a rodhousing 884 that defines a cylindrical channel 886 sized and shaped toreceive a rod 888, which is slidable within channel 886 relative to rodhousing 884. Rod housing 884 also defines bore holes 898 configured toreceive pins 882.

Rod 888 defines two slots 916 through which pins 882 pass. The slots 916limit axial movement of the rod 888 relative to rod housing 884 alongaxis B to a maximum displacement distance L1 approximately equal to thewidth of the slots minus the diameter of pins 882. At one end, rod 888includes a threaded segment 918 and an end segment 920 defining a groove922 that accepts a retaining ring 924. At the other end, rod 888 has arod end 930 defining a groove 932 that accepts a retaining ring 934.

Rod housing 884 includes a first mating end 890 and a second mating end892. First mating end 890 is coupled to a knurled knob assembly 894, andsecond mating end 892 is coupled to a knob assembly 896. First matingend 890 includes a mating surface 891 and alignment posts 900. Secondmating end 892 includes a mating surface 893 and alignment posts 908.Knurled knob assembly 894 includes a mating plate 902 having a matingsurface 901, which mates with surface 891 of end 890, and a knurled knob928 having a threaded post 926 into which threaded segment 918 of rod888 is screwed. Knob assembly 896 includes a knob 910 having a matingsurface 909, which mates with surface 893 of end 892, and a non-threadedpost 957 defining a bore 954 that receives rod end 930.

Knurled knob 928 has a base 937 defining a cavity 936 partially boundedby a threaded portion 940 that receives a threaded end plug 938.Threaded segment 918 of rod 888 extends through post 926 and into cavity936. Mating plate 902 is positioned between first mating end 890 andknurled knob 928. Referring to FIG. 20A, mating plate 902 defines a borehole 946 through which post 926 passes, and two recesses 948 that eachaccept an alignment post 900 and two recesses 948 a that each accept aspring 906. Alignment posts 900 limits any rotation between mating plate902 and mating end 890, and springs 906 are compression springs, whichact between mating surfaces 891 and 901.

Knob 910 has a base 956 defining a cavity 952 partially bounded by athreaded portion 960 that receives a plug 958. Referring to FIG. 20B,knob 910 defines two recesses 948 b that each accept an alignment post908 and two additional recesses 948 c that each accept a spring 914.Alignment posts 908 limits any rotation between knob 910 and mating end892, and springs 914 are compression springs, which act between matingsurfaces 893 and 909.

With knurled knob 928 fully screwed onto threaded segment 918 of rod888, rod 888 is fixed in place with the respective mating surfacesengaged. When knurled knob 928 is loosened, rod 888 can move along axisB with slots 916 sliding along pins 882. Springs 906, 914 act to centerrod 888 between the knob assemblies 894, 896, and retaining rings 924,934 hold knobs 928, 910 onto the knob assemblies by contacting bases937, 956, respectively. In use, turning knob 928 loosens both knobs suchthat suture or other material to be retained can be positioned betweenthe mating surfaces of both knobs. Tightening knob 928 in turn tightensboth knobs to secure the suture in place. Both sutures are thus secured,one to each end of a rod assembly 876 of tie rod assembly 870, atsubstantially the same time through the turning of a single knob (i.e.,the knurled knob). Securing the sutures simultaneously and with only oneknob decreases the number of “hands” involved in this surgical step.

While the implementation of the tie rod assembly 870 shown in FIGS.18-20 has two parallel rod assemblies 876, other implementations canhave only one rod assembly 876 or more than two rod assemblies 876,depending upon the number of strands of soft tissue to be implanted inthe bone tunnel.

Referring to FIG. 21, handle assembly 872 includes a handle section 970,a sleeve 1006, and an inner shaft assembly 974 coupling handle section970 to sleeve 1006. Handle section 970 defines a slot 989 and innershaft assembly 974 has a pin 986 that slides within slot 989 such thathandle section 970 can be moved relative to inner shaft assembly 974.Sleeve 1006 defines a slot 1012 and inner shaft assembly 974 has a pin1004 that slides within slot 1012 such that sleeve 1006 can be movedrelative to inner shaft assembly 974. Handle section 970 has a handle970 a and a tubular extension 970 b.

Referring to FIG. 22, handle section 970 defines a through bore 972sized and shaped to receive inner shaft assembly 974. Sleeve 1006defines a through bore 1008 for receiving handle tubular extension 970 band inner shaft assembly 974. Inner shaft assembly 974 includes a shaft976 and an end piece 991 coupled to shaft 976 by a pin 998. Bore 972 hasan enlarged region 973 in which is positioned a spring 978 surroundingshaft 976. Spring 978 is positioned on shaft 976 between a shelf 990 ofshaft 976 and a bushing 980. Bushing 980 is positioned next to aretaining ring 982 which is attached to handle 970 and slidable relativeto inner shaft assembly 974. Positioned within sleeve 1008 and abuttinga distal end 970 c of handle section 970 and a shelf 976 a of shaft 976is a washer 984. Also positioned within sleeve 1008 between washer 984and a shelf 1010 of sleeve 1006 is a second spring 1014.

Referring to FIG. 23, end piece 991 includes a cylindrical member 992and a coupler 994. Cylindrical member 992 defines a bore hole 996 forreceiving pin 998 to couple cylindrical member 992 to shaft 976. Coupler994 defines a slot 1000 for coupling handle assembly 872 to arch 880,and a bore hole 1002 that receives a pin 1004.

The handle assembly 872 is attached to the tie rod assembly 870 bypulling sleeve 1006 in the direction of arrow P relative to the handle970. Pulling sleeve 1006 compresses spring 1014 and exposes couplingslot 1000 of coupler 994. Arch 880 of tie rod assembly 870 is theninserted into coupling slot 1000. Once arch 880 is inserted into slot1000, the pulling force is removed and spring 1014 automaticallyretracts the coupler 994 back into the sleeve 1006. Pin 1004 keepssleeve 1006 from sliding distally off handle 970 and inner shaftassembly 974.

Movement of handle 970 relative to inner shaft assembly 974 against theforce of spring 978 provides an indication of tension applied to handle970 when handle assembly 872 is coupled to tie rod assembly 870. Thisrelative movement causes pin 986 to slide along slot 989. Slot 989 ismarked accordingly to relate the movement of pin 986 to a tensile load(e.g., 1-100 Newtons). When a tensile load is imparted to tie rodassembly 870 via coupler 994, spring 978 is compressed between retainingring 982 attached to handle 970 and shelf 990 of inner shaft 976.Compression of spring 978 results in movement of handle 970 relative toinner shaft 976 and, thereby results in movement of tension indicatorpin 986 (attached to shaft 976) relative to slot 989 (defined by handle970). A greater tensile load results in a greater compression of spring978, a correspondingly greater displacement of tension indicator pin 986relative to slot 989, and therefore, a greater measurement of tension.

Referring to FIGS. 16 and 24, tensioning device 712 is attached to board708 using device holder 714 and coupler 812. Tensioning device holder714 includes a body 1020 with a vertical member 1022 from which extendsa small arm 1024 and a base arm 1026. Small arm 1024 has a lip 1025sized and shaped to fit within hole 878 of frame 874 (FIG. 18) such thatone of the rod assemblies 876 can be positioned on a surface 1027 of arm1024. Base arm 1026 defines a groove 1029 in which the other rodassembly 876 is positioned. Device holder 714 includes a plug 1028attached to base arm 1026 by a pin 1030. Tensioning device holder 714 isattached to board 708 by inserting plug 1028 into coupler 812.

FIG. 25 shows a detailed flow diagram of a specific implementation 1100of surgical process 600 using kit 700 directed to ACL repair. Operations1110, 1120, 1130, 1140, and 1150 correspond to operations 610, 620, 630,640, and 650, respectively.

Referring also to FIGS. 26A and 26B, initially, harvested semitendinosusand gracilis tendons 802 are sutured, folded, and inserted through asuture loop 1221 that couples the tendons to an ENDOBUTTON™ 1220. Theoperator attaches ENDOBUTTON™ 1220 to ENDOBUTTON™ loop 804, and placesthe tendons on scale extender 710 of graft positioning board 708 (1112).The operator then threads the gracilis tendon ends 1200 a, 1200 bthrough guide tubes 756 a and 756 b of sheath assembly 703 (1114) usingattached sutures 1202.

The operator measures the depth of the tibial and femur tunnels usingmeasurement device 704 (1120). The depth of the bone tunnels is measuredby inserting rod 707 of measurement device 704 into the bone tunnelsuntil the distal end of the cylindrical probe rod reaches the end of thebone tunnels. The operator then advances adjustable stop 706 up to thebone tunnel entrance by sliding stop 706 along rod 707, and securesadjustable stop 706 in position using thumb screw 766. Rod 707 is thenremoved from the bone tunnels, and the distance between stop 706 and thedistal end of the rod corresponds to the bone tunnel depth. This depthmeasurement can be done at any time prior to operation 1138 (i.e., priorto adjusting the position of the sheath 703 and fixing it in position).

Referring to FIG. 27, the operator couples sutures 1202 attached totendon ends (e.g., gracilis tendon ends) 1200 a, 1200 b to tensioningdevice 712 mounted on tensioning device holder 714 (1132). Tensioningdevice holder 714 is fixed in any position along guide rail 814 thatprovides a distance between the tensioning device 712 and the sheath 702that conveniently allows subsequent insertion of tapered screw 718 intothe bone tunnel. First knurled knob 928 is loosened, and one suture 1202a is positioned between knurled knob 928 and mating plate 902, and asecond suture 202 b is positioned between knob 910 and mating surface893 (FIG. 19). Once both sutures are in position, the operator uses onehand to pull both sutures to the point where there is no slack in thesutures and the other hand to tighten knurled knob 928 to secure bothsutures to tensioning device 712.

Referring to FIG. 28, the operator then positions sheath 702 relative tografts 802 such that the distance between ENDOBUTTON™ loop 804 and theproximal end 702 a of sheath 702 corresponds to the measured bone tunneldepth (1138). The guide tubes 756 a and 756 b are then removed fromgrafts 802, and tie suture 758 is used to fix sheath 702 in placerelative to grafts 802 (FIG. 29).

Referring to FIG. 30, the operator then couples sutures 1204 attached tothe two ends of the semitendinosus tendon 802 a to the tensioning device712 as discussed above with reference to FIG. 27.

Referring to FIGS. 31A and 31B, the operator removes the soft tissuegraft assembly 1160, which includes ENDOBUTTON™ 1220, the tendons,sheath 702, and tensioning device 712, from graft positioning board 708(1142), and attaches one or more sutures 1222 to ENDOBUTTON™ 1220 (FIG.32). The operator then inserts sutures 1222 and ENDOBUTTON™ 1220 intothe tibial tunnel and pulls on sutures 1222 using a block 1162 toposition the tendons within the bone tunnels (1144). Block 1162 providesa mechanical advantage that facilitates pulling the ENDOBUTTON™ loop,the tendons and the sheath 702 through the bone tunnels.

Referring to FIGS. 33A and 33B, once sheath 702 is pulled into positionsuch that end 702 a of sheath 702 is flush with the entrance to thetibial bone tunnel, the operator inserts a guide wire (not shown) intofunneled end 757 of guide wire tube 756 c, removes guide wire tube 756 cby sliding the guide wire tube out of tube 752 c of sheath 702 and overthe guide wire, and then advances a tapered interference screw 718 overthe guide wire and into tube 752 c using screw driver 716 (1150). Duringadvancement of the screw, the operator maintains the desired tension onthe tendons by pulling on handle assembly 970 while monitoring theposition of the tension indicator pin 986 in slot 989. Use of thetensioning device during screw advancement provides the advantage ofequalizing the tension of the tendons and organizing the tendons tofacilitate accurate positioning of the interference screw 718 in tube752 c of sheath 702. Driver 716 is conveniently inserted through hole878 of the tensioning device.

Referring to FIG. 34, when in position, ENDOBUTTON™ 1220 is on thesurface 1228 of femur 1180, suture loop 1221 extends into the femurtunnel 1230, grafts 802 extend from suture loop 1221 in the femur tunnelto the tunnel 1232 in tibia 1182, and sheath 702 with interference screw718 are flush with the surface 1234 of the tibia. The gracilis tendongrafts and their surrounding tubes 752 a and 752 b as well as thesemitendinosus tendons are compressed between screw 718 (located in tube752 c) and the wall 1236 of the bone tunnel 1232 to fix the graftswithin the bone tunnel.

The sheaths need not be used exclusively with bone screws. The sheathscan be used to improve fixation of other types of implantable fixationdevices, such as soft tissue tacks, plugs, and suture anchors. The sizeand shapes of the sheaths can be varied to accommodate the differenttypes of fixation devices. The sheaths need not be used in bone tunnels.For example, soft tissue can be positioned inside a sheath, and thesheath attached to the side of a bone with a fixation device such as atack.

Knurled knob 928 need not be knurled. Knob 928 can instead have adifferent type of grippable surface that allows application of atorsional load without slipping (e.g., a scalloped or octagonalsurface).

Tensioning device 712, scale extender element 710, and adjustable stop706 need not be used solely for soft tissue grafts but can instead beused for bone-tendon-bone grafts.

The displacement of sleeve 1008 relative to handle 970 can be used toindicate tension by adding scale markings to handle 970. The sliding ofhandle 970 relative to sleeve 1008 provides an indication similar tothat provided by the sliding of pin 986 in slot 989. The relativemovement causes the scale markings on handle 970 to be exposed and toindicate the applied tension.

The process 1100 can be used for achilles tendons, fascia lata, or otherharvested tendons. The ENDOBUTTON™ or ENDOBUTTON™ loop of process 1100may be replaced by an additional bone screw, a suture through a washer,a suture button, or a post.

1. An assembly, comprising: a sheath for organizing soft tissue,including a fixation device including a shaft; a first tube including aflexible body sized and shaped to conform to the shape of the shaft ofthe fixation device when the fixation device is received therein; and atleast one second tube coupled to the first tube, the second tubeincluding a flexible body sized and shaped to receive a soft tissuegraft; wherein an outermost surface of the sheath is formed by thetubes.
 2. The assembly of claim 1, wherein the sheath includes a thirdtube coupled to the first tube, the third tube including a flexible bodysized and shaped to receive a soft tissue graft.
 3. The sheath of claim2 wherein the first tube has a different diameter than the second andthird tubes.
 4. The sheath of claim 3 wherein the second and third tubeshave the same diameter.
 5. The sheath of claim 2 wherein the second andthird tubes have the same diameter.
 6. The sheath of claim 5 wherein thefirst tube has the same diameter as the second and third.
 7. Theassembly of claim 1, wherein at least one of the first tube and secondtube comprise a biocompatible material selected from the groupconsisting of hydroxyapatite, polylactic acid, and polylactic glycolicacid.
 8. The assembly of claim 1, further comprising a guide disposedwithin the second tube for facilitating threading of soft tissue throughthe second tube.
 9. The assembly of claim 1, further comprising a guidedisposed within the first tube for facilitating advancement of a guidewire though the first tube.
 10. The assembly of claim 9, wherein one endof the guide has a funneled shape.
 11. The assembly of claim 1, whereinthe first tube and the second tube are integrally formed.
 12. Theassembly of claim 1, wherein the flexible body of the first tubecomprises strands that form a mesh structure, the strands definingspaces therebetween.
 13. The assembly of claim 1, wherein the flexiblebody of the second tube comprises strands that form a mesh structure,the strands defining spaces therebetween.
 14. The assembly of claim 1,wherein the flexible body of the first tube includes a relieved wall.15. The assembly of claim 14, wherein a major portion of the relievedwall is open.
 16. The assembly of claim 1, wherein the relieved wall isperforated.
 17. The assembly of claim 1, wherein the relieved walldefines a plurality of holes therethrough.
 18. The assembly of claim 1,wherein the flexible body of the second tube includes a relieved wall.19. The assembly of claim 18, wherein the relieved wall is perforated.20. The assembly of claim 18, wherein the relieved wall defines aplurality of holes therethrough.
 21. The assembly of claim 18, wherein amajor portion of the relieved wall is open.
 22. The assembly of claim 1,wherein the flexible body of the second tube has two ends, each endhaving an opening.
 23. The assembly of claim 22, wherein the openingshave substantially the same dimensions.
 24. The assembly of claim 22,wherein the openings are circular.
 25. The assembly of claim 1, whereinthe first tube is smaller in diameter than the second tube.
 26. Theassembly of claim 1, further comprising a securing element for securingthe second tube to the soft tissue graft.
 27. The assembly of claim 1,wherein the fixation device comprises a bone screw.
 28. The assembly ofclaim 1 further comprising a third tube coupled to the first tube, thethird tube including a flexible body sized and shaped to receive a softtissue graft.
 29. The assembly of claim 28 wherein the first tube has adifferent diameter than the second and third tubes.
 30. The assembly ofclaim 29 wherein the second and third tubes have the same diameter. 31.The assembly of claim 28 wherein the second and third tubes have thesame diameter.
 32. The assembly of claim 31 wherein the first tube hasthe same diameter as the second and third tubes.
 33. The assembly ofclaim 1 further comprising a member coupling the first tube with thesecond tube.
 34. The assembly of claim 33 wherein the member comprises asuture.
 35. The assembly of claim 1 further comprising a suture couplingthe first tube with the second tube.